U.S. patent number 9,157,144 [Application Number 12/652,340] was granted by the patent office on 2015-10-13 for masking mechanism for film forming apparatus.
This patent grant is currently assigned to JAPAN SCIENCE AND TECHNOLOGY AGENCY. The grantee listed for this patent is Hideomi Koinuma, Yuji Matsumoto, Ryota Takahashi, Yukio Yamamoto. Invention is credited to Hideomi Koinuma, Yuji Matsumoto, Ryota Takahashi, Yukio Yamamoto.
United States Patent |
9,157,144 |
Koinuma , et al. |
October 13, 2015 |
Masking mechanism for film forming apparatus
Abstract
It comprises a mask (11) having a first, a second and a third
action edge (11a, 11b, 11c), and a drive means for moving the mask
(11) relative to a substrate (12) in a uniaxial direction (A)
whereby moving the mask at a fixed rate of movement to cause the
edges to successively act on an identical substrate region while
successively applying different materials thereto forms thin films
of three components successively with respective film thickness
gradients oriented in three different directions mutually angularly
spaced apart by an angle of 120.degree. to allow these films to
overlap, thereby forming a ternary phase diagrammatic thin film
13.
Inventors: |
Koinuma; Hideomi (Tokyo,
JP), Yamamoto; Yukio (Kanagawa, JP),
Matsumoto; Yuji (Kanagawa, JP), Takahashi; Ryota
(Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Koinuma; Hideomi
Yamamoto; Yukio
Matsumoto; Yuji
Takahashi; Ryota |
Tokyo
Kanagawa
Kanagawa
Tokyo |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
JAPAN SCIENCE AND TECHNOLOGY
AGENCY (Saitama, JP)
|
Family
ID: |
32025027 |
Appl.
No.: |
12/652,340 |
Filed: |
January 5, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100151128 A1 |
Jun 17, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10528265 |
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PCT/JP03/11950 |
Sep 19, 2003 |
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Foreign Application Priority Data
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Sep 20, 2002 [JP] |
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2002-275365 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C
14/044 (20130101) |
Current International
Class: |
C23C
16/00 (20060101); C23C 14/04 (20060101) |
Field of
Search: |
;427/248.1-255.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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43-27926 |
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Dec 1968 |
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JP |
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49-42155-01 |
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Apr 1974 |
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JP |
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49-34573 |
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Sep 1974 |
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JP |
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60-181264 |
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Sep 1985 |
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JP |
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2004-35983 |
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Feb 2004 |
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JP |
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Other References
European Search Report dated Dec. 19, 2008 issued in corresponding
Application No. 03797681.8. cited by applicant .
C. J. Bowler and R. D. Gould, "A sequential masking system for the
deposition of multilayer thin-film structures" Journal of Vacuum
Science Technology, 1987, pp. 114-115, XP001308318 Woodbury, NY,
USA. cited by applicant .
Earl Danielson et al,"A combinatorial approach to the discovery and
optimization of luminescent materials" Nature, Oct. 30, 1997, vol.
389, pp. 944-948. cited by applicant .
X.-D. Xiang et al., "A combinatorial approach to materials
discovery" Science, Jun. 23, 1995, vol. 268, pp. 1738-1740. cited
by applicant .
Hideomi Koinuma, "Combinatorial materials research projects in
Japan" Applied Surface Science, Apr. 28, 2002, vol. 189, pp.
179-187. cited by applicant .
Yuji Matsumoto, "Advance combinatorial thin film technology for new
functional materials" Tokyo, Japan, Mar. 27, 2003, No. 0, p. 16.
cited by applicant .
International Search Report of PCT/JP03/11950, mailing date of Nov.
4, 2003. cited by applicant.
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Primary Examiner: Wieczorek; Michael
Assistant Examiner: Miller; Michael G
Attorney, Agent or Firm: Westerman, Hattori, Daniels &
Adrian, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional application of U.S. Ser. No.
10/528,265, filed Mar. 17, 2005, which is a National Phase filing
of PCT/JP03/11950, filed Sep. 19, 2003, which is based upon and
claims the benefit of priority from the prior Japanese Patent
Application No. 2002-275365, filed Sep. 20, 2002, the entire
contents of which are hereby incorporated by reference.
Claims
What is claimed is:
1. A method of making thin film using a masking mechanism, the
masking mechanism comprising: a mask; and a means for moving the
mask in one direction on a straight line above or beneath a
substrate; wherein the mask has a periphery making an angle of
.alpha. (where 0.degree.<.alpha.<90.degree.) to the straight
line, and a first and a second openings, the first opening has a
first edge making an angle of 30.degree.+.alpha. to the straight
line, the second opening has a second edge making an angle of
-30.degree.+.alpha. to the straight line, the periphery, the first
edge and the second edge are arranged along the one direction on
the straight line, and further including the steps of: positioning
the periphery of the mask immediately before a region of
equilateral triangle where a thin film of ternary
phase-diagrammatic system is to be formed in the substrate, moving
the mask linearly in the same direction as the one direction, while
a first material is evaporated so that the periphery forms a
film-thickness gradient of the first material, moving the mask
linearly and continuously in the same direction as the one
direction, until the first edge of the mask is positioned
immediately before the region of equilateral triangle where the
thin film of ternary phase-diagrammatic system is to be formed in
the substrate, moving the mask linearly in the same or opposite
direction to the one direction, while a second material is
evaporated so that the first edge of the mask forms a
film-thickness gradient of the second material, moving the mask
linearly and continuously in the same direction as the one
direction, until the second edge of the mask is positioned
immediately before the region of equilateral triangle where the
thin film of ternary phase-diagrammatic system is to be formed in
the substrate, and moving the mask linearly in the same or opposite
direction to the one direction, while a third material is
evaporated so that the second edge of the mask forms a
film-thickness gradient of the third material.
2. A method of making thin film using a masking mechanism, the
masking mechanism comprising: a mask; and a means for moving the
mask in one direction on a straight line above or beneath a
substrate; wherein the mask has a periphery orthogonal to the
straight line, and a first and a second openings, the first opening
has a first edge making an angle of 30.degree. to the straight
line, the second opening has a second edge making an angle of
-30.degree. to the straight line, the periphery, the first edge and
the second edge are arranged along the one direction on the
straight line, and further including the steps of: positioning the
periphery of the mask immediately before a region of equilateral
triangle where a thin film of ternary phase-diagrammatic system is
to be formed in the substrate, moving the mask linearly in the same
direction as the one direction, while a first material is
evaporated so that the periphery forms a film-thickness gradient of
the first material, moving the mask linearly and continuously in
the same direction as the one direction, until the first edge of
the mask is positioned immediately before the region of equilateral
triangle where the thin film of ternary phase-diagrammatic system
is to be formed in the substrate, moving the mask linearly in the
same or opposite direction to the one direction, while a second
material is evaporated so that the first edge of the mask forms a
film-thickness gradient of the second material, moving the mask
linearly and continuously in the same direction as the one
direction, until the second edge of the mask is positioned
immediately before the region of equilateral triangle where the
thin film of ternary phase-diagrammatic system is to be formed in
the substrate, and moving the mask linearly in the same or opposite
direction to the one direction, while a third material is
evaporated so that the second edge of the mask forms a
film-thickness gradient of the third material.
3. The method of making a film as set forth in claim 1 or 2,
wherein the periphery has a length larger than a side of the region
of equilateral triangle, the first opening has a size larger than
the region of equilateral triangle, and the second opening has a
size larger than the region of equilateral triangle.
4. The method of making a film as set forth in claim 1 or 2,
wherein the first opening is arranged between the first edge and
the second edge, and the second edge is arranged between the first
and second opening.
Description
TECHNICAL FIELD
The present invention relates to a masking mechanism or device for
a film forming apparatus for the purpose of making a thin film of
compositions corresponding to a ternary phase diagram.
BACKGROUND ART
In recent years a number of new physical phenomena such as those of
high temperature superconducting, giant magnetic resistance, high
intensity fluorescence and catalysis have been discovered.
Exploring a material and composition that develops such a physical
phenomenon is carried out with a combinatorial film forming
apparatus in order to reduce the time expended for material
investigation. Using a combinatorial film forming apparatus allows
forming a library of a group of materials possible of that
developing on one substrate in one vacuum process and finding a new
material and a new composition from the library or deriving a
theoretical prediction from a specific character of the library. It
is said that the use of a combinatorial film forming apparatus can
shorten the time period of a hundred years thus far spent to a
month, for a material exploration.
A combinatorial film forming apparatus makes it essential to
include a means for limiting supply of materials electively to a
desired portion on a substrate, a film forming means for depositing
films of different kind and a structural analysis means for
analyzing the structure of films of desired portion on the
substrate. For example, an apparatus which uses a ablation laser
for film deposition, is equipped with a plurality of masking units,
a target switching unit, an ablation laser light lead-in unit, a
substrate heating laser unit and a reflection high-energy electron
diffraction (RHEED) unit.
And, in late years demands to find new materials of binary and
ternary systems have been rising. For instance, a fluorescent
material for a plasma display, which is required to possess
properties different from those of a conventional electron-beam
excited fluorescent material, is predicted to be realized by a new
material of binary or ternary system.
Materials of binary and ternary systems have so far been
investigated using a combinatorial film forming arrangements as
shown in FIG. 22. FIG. 22 shows diagrammatically methods of
investigating materials of binary and ternary systems with the
conventional combinatorial deposition arrangements. As shown in
FIG. 22(a), there are prepared a first mask 1 having a number of
unmasking apertures for defining a plurality of independent
specimens on a substrate, to wit to form pixels on the substrate
and a second mask 2 in the form of a masking shield for selectively
covering the unmasking apertures to select the pixels to be formed
by vapor deposition. The relative position among the substrate, the
first mask 1 and second mask 2 is adjusted to select the pixels to
be formed, while a material forming the pixel by vapor deposition
is selected, and this step is repeated so as to form on the
substrate thin films that are of a binary or ternary
phase-diagrammatic system which has predetermined ratios of
components varied from pixel to pixel. Then, the pixels made are
measured as to their specified properties to find out a pixel
having particular properties as desired and then to determine from
its ratio of components an optimum ratio of components that is
required to achieve specific properties as desired.
As shown in FIG. 22(b), there is also used a rotary disk having a
plurality of masks thereon, each of which are arranged to select
pixels to be formed by vapor deposition, and this rotary disk is
successively rotated while a material forming pixels is selected to
form pixels on a substrate, which have predetermined ratios of
components differing from pixel to pixel to form binary or ternary
phase-diagrammatic system. Then, the pixels made are measured as to
their specified properties to find out a pixel having particular
properties as desired and then to determine from its ratio of
components an optimum ratio of components that is required to
achieve specific properties as desired.
By the way, there is a material, such as a fluorescent material,
which exhibits useful properties only in an extremely narrow rage
of its ratio of components. Such a case requires the conventional
methods to form an extremely large number of pixels with finely
varied ratios of components. In the prior method shown in FIG.
22(a), as the method requires the precise positioning among the
substrate, the first mask 1 and second mask 2, however, this in
turn requires spending considerable time, and in addition, as a
result of which if an extremely large number of pixels are to be
formed, then the film depositing conditions tend to change between
the first and the last formed pixels. Thus, for example, the
substrate temperature distribution and atmospheric composition
could change uncontrollably with the lapse of time, giving rise to
the problem that reproducible data, or reliable data can no longer
be obtained.
And, while in the prior method shown in FIG. 22(b) rotation makes
it sufficient to position a given mask in less time-consuming,
there the limitation in volume of the vacuum unit limits the number
of masks that can be mounted and it is thus difficult to form an
extremely large number of pixels with finely varied ratios of
components. For this reason, where an extremely large number of
pixels with finely varied ratios of components must be formed, the
prior art must have relied on a technique as mentioned below as
regards a binary system.
FIG. 23 diagrammatically shows a conventional method of making a
thin film that is binary phase diagrammatic. As shown at (a) of the
Figure, there are used a first mask 1 disposed perpendicular to a
flow of vapor of material A or B and having an opening, a second
mask 2 in the form of a masking shield movable in a scanning manner
parallel to the first mask 1 and a substrate disposed across the
opening of the first mask 1. In operation, as shown in (b) the mask
2 is moved in the direction of x while material A is being
vaporized. Since moving the mask 2 at a constant speed in the
direction of x causes material A vapor-deposited on a region of the
substrate to become thicker in proportion to the time in which it
is exposed to the flow of vapor of material A, there is obtained a
thickness distribution of material A that increases at a given
gradient in the direction of movement, namely in the direction of
x. Thereafter, if as shown at (c) the material for vapor deposition
is replaced with material B and the mask 2 is moved in a scanning
manner from the position opposite to that shown in FIG. 23(b) and
in the direction of -x, there is then obtained a thickness
distribution of material B that increases at a given gradient in
the direction of movement, namely in the direction of -x. As shown
at the right hand side of (c), there is thus obtained a combined
thickness distribution of materials A and B made up of a film of
material A whose thickness varies continuously from 0 to 100% and a
film of material B whose thickness varies continuously from 100 to
0% in the direction of x. The materials A and B vapor-deposited are
each extremely thin in film thickness and when coming into contact
with each other are immediately mixed together into a stable state
of binary material that is determined by the substrate temperature.
Repeating the vapor deposition of A followed by the vapor
deposition of B allows forming a thin film that is binary phase
diagrammatic of a desired thickness.
This method permits obtaining a binary phase diagramming thin film
in which its ratio of components continuously varies or is varied
finely in the direction of x and also obtaining reliable data since
the thin film can be made in an extremely short period of time.
This method in a sense can be said to be a method of forming by
uniaxial movement of a single mask having an opening relative to a
substrate. Further, it can be said to be a method of forming by
uniaxial movement of one side of the opening in the mask, namely
uniaxial movement of a edge of the mask relative to the substrate.
It will be apparent that this method can be expanded to form a
ternary phase diagramming thin film by moving a mask edge
triaxially or along three axes mutually intersecting at an angle of
120 degrees.
It is extremely difficult, however, to include such a triaxially
operating masking mechanism that must necessarily become
considerably large in volume in an apparatus of this type used for
material exploration, e.g., in a combinatorial film forming
apparatus that makes it essential to be equipped with an ablation
laser light lead-in unit, a target switching unit, a substrate
heating laser unit and a reflection high-energy electron
diffraction unit in a vacuum chamber. This can be done, of course,
by making the vacuum chamber in volume to an extent necessary to
accommodate them, but so enlarging it requires augmenting the
capacity of its vacuum pumping system correspondingly, thus making
the apparatus highly costly.
DISCLOSURE OF THE INVENTION
In view of the problems mentioned above it is an object of the
present invention to provide a masking mechanism or device for a
film forming apparatus that is capable of making a thin film of a
ternary phase diagrammatic system without making the apparatus
costly.
In order to achieve the object mentioned above there is provided in
accordance with the present invention a masking mechanism or device
for a film forming apparatus, characterized in that: it comprises a
single mask and a means for moving the mask relative to a substrate
in a uniaxial direction; and the said mask has a first, a second
and a third single action edge each of which has a normal unit
vector; wherein: the normal unit vector of the said first single
action edge and that of the said second single action edge make an
angle of 120.degree. relative to each other, the normal unit vector
of the said second single action edge and that of the said third
single action edge make an angle of 120.degree. relative to each
other, and the normal unit vector of the said third single action
edge and that of the said first single action edge make an angle of
120.degree. relative to each other.
According to this device construction of the present invention, the
first single action edge is positioned immediately ahead of a
substrate region where a ternary phase diagrammatic thin film is to
be formed. Then, the first single action edge may be moved at a
selected rate of movement while the substrate region is
vapor-deposited with a first material to produce a film thickness
gradient of the first material. Next, the second single action edge
is positioned immediately ahead of the substrate region to be
formed with the ternary phase diagrammatic thin film. Then, the
second single action edge may be moved at a selected rate of
movement while the substrate region is vapor-deposited with a
second material to produce a film thickness gradient of the second
material. Next, the third single action edge is positioned
immediately ahead of the substrate region to be formed with the
ternary phase diagrammatic thin film. Then, the third single action
edge may be moved at a selected rate of movement while the
substrate region is vapor-deposited with a third material to
produce a film thickness gradient of the third material. With the
first, second and third action edges oriented by making 120.degree.
with one another, these film thickness gradients that then develop
makes 120.degree. with one another, thereby forming a thin film of
the ternary phase diagrammatic system from component thin films.
The masking mechanism for a film forming apparatus according to the
present invention entails only a single mask and a means whereby
the mask can only be moved in a single axial direction and hence
requires a minimum of its volume and size. With the capability of
forming a thin film of a ternary phase diagrammatic system, it no
longer makes it necessary to raise the equipment cost.
Here, the term "single action edge" is intended herein to mean an
edge portion of the mask that acts to produce a film thickness
gradient with one edge of the mask. Likewise, the "double action
edge" is intended herein to mean an edge portion of the mask that
acts to produce a film thickness gradient with two edges of the
mask and "triple action edge" herein to mean an edge portion of the
mask that acts to produce a film thickness gradient with three
edges of the mask.
Specifically, the said single mask has a side making an angle of
90.degree.+.alpha. (where
0.degree..ltoreq..alpha.<90.degree.)relative to the said
uniaxial direction, and the said mask has a first and a second
opening, wherein the said first opening has a side making an angle
of 30.degree.+.alpha. relative to the said uniaxial direction and
the said second opening has a side making an angle of -30
.degree.+.alpha. relative to the said uniaxial direction, and the
said side making an angle of 90.degree.+.alpha. relative to said
uniaxial direction constitutes the said first single action edge,
the said side making an angle of 30.degree.+.alpha. relative to the
said uniaxial direction constitutes the said second single action
edge, and the said side making an angle of -30.degree.+.alpha.
relative to the said uniaxial direction constitutes the said third
single action edge.
According to this specific feature of the invention, as the normal
unit vectors of the first, second and third single edges mutually
make an angle of 120.degree., a thin film of a ternary phase
diagrammatic system can be obtained.
Also, the said single mask may specifically comprise a single disk.
Then, this disk has a first, a second and a third cutout, and the
said first cutout has a side making an angle of 90.degree.+.alpha.
(where 0.degree..ltoreq..alpha.<90.degree.) relative to a
circumferential direction of the said disk, the said second cutout
has a side making an angle of 30.degree.+.alpha. relative to the
circumferential direction of the said disk and the said third
cutout has a side making an angle of -30.degree.+.alpha. relative
to the said circumferential direction of the said disk, wherein the
said side making an angle of 90.degree.+.alpha. relative to the
circumferential direction of the said mask constitutes the said
first single action edge, the said side making an angle of
30.degree.+.alpha. relative to the circumferential direction of
said disk constitutes the said second single action edge, and the
said side making an angle of -30.degree.+.alpha. relative to the
circumferential direction of the said disk constitutes the said
third single action edge. This disk can be rotated about its center
axis to give rise to a thin film of a ternary phase diagrammatic
system as mentioned above.
The present invention also provides in a second form of
implementation thereof a masking mechanism or device for a film
forming apparatus, characterized in that it comprises a single mask
and a means for moving the mask relative to a substrate in a
uniaxial direction; and the said mask has a first and a second
single action edge and a double action edge in the form of a
triangle having its base oriented in the said uniaxial direction
and its two other sides constituting action edges, wherein the
normal unit vector of the said first single action edge makes an
angle of 30.degree. relative to the said uniaxial direction and the
normal unit vector of the said second single action edge makes
-30.degree. relative to the said uniaxial direction.
According to this device construction of the present invention, the
first single action edge is positioned immediately ahead of a
region on a substrate where a ternary phase diagrammatic thin film
is to be formed. Then, the first single action edge may be moved at
a selected rate of movement while the substrate region is
vapor-deposited with a first material to produce a film thickness
gradient of the first material. Next, the second single action edge
is positioned immediately ahead of the substrate region to be
formed with the ternary phase diagrammatic thin film. Then, the
second single action edge may be moved at a selected rate of
movement while the substrate region is vapor-deposited with a
second material to produce a film thickness gradient of the second
material. Next, the triangular double action edge is positioned
immediately ahead of the substrate region to be formed with the
ternary phase diagrammatic thin film. Then, the triangular double
action edge may be moved at a selected rate of movement while the
substrate region is vapor-deposited with a third material to
produce a film thickness gradient of the third material. In this
case, the film thickness gradient produced by means of the
triangular double action edge extends perpendicular to the
direction in which the mask is moved and the film thickness
gradients produced by means of the first and second single action
edges make an angle of 120.degree. with one another, thereby
forming a thin film of the ternary phase diagrammatic system from
component thin films. The masking mechanism for a film forming
apparatus according to the second form of implementation of the
present invention entails, here again, only a single mask and a
means whereby the mask can only be moved in a single axial
direction and hence requires a minimum of its volume and size. With
the capability of forming a thin film of a ternary phase
diagrammatic system, it does not make it necessary to raise the
equipment cost.
Specifically, the said single mask may comprise a single disk.
Then, this disk has a first and a second cutout, and the said first
cutout is a cutout in the form of a fan having its two sides making
angles of 30.degree. and -30.degree. relative to a circumferential
direction of the said disk, respectively, and the said second
cutout is a cutout having sides making angles of 60.degree. and
-60.degree. relative to the circumferential direction of the said
disk, respectively, and a side oriented parallel to the said
circumferential direction.
The present invention also provides in a third form of
implementation thereof a masking mechanism or device for a film
forming apparatus, characterized in that: it comprises a single
mask and a means for moving the mask relative to a substrate in a
uniaxial direction; and the said mask has a triangular opening
having a base side oriented in a said uniaxial direction, the said
mask also having a side extending orthogonal to the said uniaxial
direction; and the other two sides other than the base side of the
said triangular opening and the said side orthogonal to the said
uniaxial direction constitute a triple action edge, whereby
selecting a rate of movement at which the said triangular opening
is moved and a rate of movement at which the said side orthogonal
to the said uniaxial direction allows a film thickness gradient to
be produced in a particular direction determined by the rates of
movement selected.
According to this device feature of the present invention, the
triangular opening is positioned immediately ahead of a region on a
substrate where a ternary phase diagrammatic thin film is to be
formed. Then, the triangular opening may be moved at a selected
rate of movement while the substrate region is vapor-deposited with
a first material. When the triangular opening has passed over the
substrate region to be formed with the ternary phase diagrammatic
thin film and the said side orthogonal to the said uniaxial
direction is positioned immediately ahead of the said substrate
region, the rate of movement is suitably altered. Since the
direction in which the thickness gradient of a thin film of the
first material which is produced in this way varies depending on
the rate at which the triangular opening is moved and the rate at
which the said side orthogonal to the said uniaxial direction is
moved, the film thickness gradient can be produced by a desired
direction by suitably selecting these rate of movement. As to a
second and a third material, too, the two rates of movement can
suitably be selected so that the directions in which the film
thickness gradients are produced for the first, second and third
materials make an angle of 120.degree. with one another, thereby
forming a thin film of the ternary phase diagrammatic system
desired. According to this method, it should be noted that since
the direction in which a film thickness gradient is produced can be
selected as desired, it is possible to form a thin film not only of
a ternary phase diagrammatic system but also of a more than three
components, multiple component phase diagrammatic system.
The masking mechanism for a film forming apparatus according to the
third form of implementation of the present invention entails, here
again, only a single mask and a means whereby the mask can only be
moved in a single axial direction and hence requires a minimum of
its volume and size. With the capability of forming a thin film of
a ternary phase diagrammatic system, it does not make it necessary
to raise the equipment cost.
Specifically, the said single mask may comprise a single disk.
Then, this disk has a first cutout, and a second cutout or a first
opening; the said first cutout is a fan shaped cutout, the said
second cutout is a cutout having a side extending orthogonal to a
circumferential direction f the said disk, and the said first
opening is a triangular opening having a base side extending
parallel to a circumferential direction of the said disk; and the
two sides of the said fan shaped cutout and the side of the said
second cutout that extends orthogonal to a circumferential
direction of the said disk constitutes the said triple action edge,
or the two sides of the said triangular opening other than the said
base side and the side of the said second cutout that extends
orthogonal to a circumferential direction of the said disk
constitutes the said triple action edge.
According to this specific feature of the present invention, simply
the rate of rotation of the disk can suitably be selected
corresponding to the said rates of displacement so that the
directions in which the film thickness gradients are produced
respectively for a first, a second and a third material, thereby
forming a thin film of a ternary phase diagrammatic system as
desired. According to this specific method as well, it should be
noted that since the direction in which a film thickness gradient
is produced can be selected as desired, it is possible to form a
thin film not only of a ternary phase diagrammatic system but also
of a more than three components, multi-component phase diagrammatic
system.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will better be understood from the following
detailed description and the drawings attached hereto showing
certain illustrative forms of implementation of the present
invention. In this connection, it should be noted that such forms
of implementation illustrated in the accompanying drawings hereof
are intended in no way to limit the present invention but to
facilitate an explanation and understanding thereof. In the
drawings,
FIG. 1 is a diagram illustrating the makeup of a masking mechanism
for a film forming apparatus that represents a first form of
implementation of the present invention;
FIG. 2 is a diagram illustrating a coordinate system in which a
mask has its face lying in an xy-plane and its thickness directed
along a z-axis and indicating a general, single action edge;
FIG. 3 is a diagram illustrating an effective movement of a single
action edge that occurs when a mask is moved;
FIG. 4 illustrates in cross sectional views typically how a thin
film is grown changing its thickness profile with a single action
edge of a mask when the mask has its moving vector +m or -m;
FIG. 5 is a diagram illustrating a thickness profile function of a
thin film formed by means of a single action edge;
FIG. 6 diagrammatically shows that a thickness gradient develops in
a thin film with a single action edge 11a in a masking mechanism as
shown in FIG. 1;
FIG. 7 diagrammatically shows that a thickness gradient develops in
a thin film with a single action edge 11b in the masking mechanism
shown in FIG. 1;
FIG. 8 diagrammatically shows that a thickness gradient develops in
a thin film with a single action edge 11c in the masking mechanism
shown in FIG. 1;
FIG. 9 is a simulated picture depicting in the thickness of black
color the thickness distribution of a thin film of ternary system
formed on a substrate by means of the masking mechanism shown in
FIG. 1;
FIG. 10 is a diagram illustrating in the makeup of components
various regions in the thin film of ternary system shown in FIG.
9;
FIG. 11 is a diagram illustrating a rotationally moving mask in a
modification of the masking mechanism shown in FIG. 1;
FIG. 12 is a partially enlarged diagram illustrating a single
action edge moving as a mask is rotated;
FIG. 13 is a diagram illustrating a position on a substrate in both
line coordinates (x, y) and polar coordinates (r, .theta.) with the
center of rotation as their origin;
FIG. 14 is a diagram illustrating the makeup of a masking mechanism
for a film forming apparatus that represents a second form of
implementation of the present invention;
FIG. 15 is a plan view illustrating the makeup of a double action
edge;
FIG. 16 is a diagram illustrating a thickness gradient of a thin
film that develops with a double action edge as shown in FIG.
15;
FIG. 17 is a diagram illustrating a thickness gradient of a thin
film that develops with a double action edge whose two edges do not
intersect with each other;
FIG. 18 is a plan view illustrating the makeup of a rotationally
moving mask as a modification of mask 31;
FIG. 19 is a diagram illustrating the makeup of a masking mechanism
for a film forming apparatus that represents a third form of
implementation of the present invention;
FIG. 20 is a plan view illustrating another example of making a
thin film of ternary system by means of the masking mechanism shown
in FIG. 19;
FIG. 21 is a plan view illustrating a modification of the masking
mechanism of FIG. 19 in which the mask is constituted by a
rotationally moving mask;
FIG. 22 schematically shows methods of investigating a binary or
ternary material according to conventional combinatorial film
forming arrangements; and
FIG. 23 schematically illustrates a conventional method of making a
thin film of binary phase diagrammatic system.
BEST MODES FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with
reference to certain suitable forms of implementation thereof
illustrated in the drawing figures.
At the outset, it should be noted that in making a thin film of a
ternary phase diagrammatic system by means of a masking mechanism
or device for a film forming apparatus according to the present
invention, the components that make up the ternary system, as in a
manner as described above in connection with the prior art for a
thin film of a binary phase-diagrammatic system, are deposited
successively on a common region on a substrate to form their
respective thin films successively on this region while controlling
the respective directions in which their thickness gradients are to
develop and this laminating step is repeated several times until
the deposited thin films in combination as a thin film of the
ternary phase diagrammatic system have a desired thickness. In
forming the composite thin film, the component thin films are
vapor-deposited each in a layer thin enough that at the time they
can be superimposed on one another by vapor deposition, their
materials can mutually diffuse from one layer to another to be
arranged with free energy minimum. Also, a maximum thickness ratio
of the component thin films is taken corresponding to the ratio of
concentration, which is equal to 1, of the components in the
ternary phase-diagrammatic system. While these premises are not
mentioned repetitiously hereinafter, it should be understood that
they always apply. Accordingly, also the term "thin film of a
ternary phase diagrammatic system" when used herein is intended to
mean a thin film constructed as mentioned above, namely the
realization of a ternary system in its phase diagram in the form of
a thin film. The particular constituent composition at a given
position in such a thin film can be known from its coordinates, and
measuring a value of a property specified for each of given
coordinate positions in the thin film to determine a coordinate
position that exhibits an optimum value of the property allows a
particular constituent composition that realizes optimally the
desired property identified and known.
FIG. 1 is a diagram illustrating the makeup of a masking mechanism
10 for a film forming apparatus that represents a first form of
implementation of the present invention. Referring to FIG. 1, the
masking mechanism 10 comprises a mask 11 supported so it can be
moved back and forth linearly as indicated by the arrow A on or
above a substrate 12. The mask 11 has a side 11a and is formed with
openings lid and 11e which have sides 11b and 11c, respectively.
the sides 11a, 11b and 11c here constituting action edges each of
which (hereinafter referred to as a "single action edge") acts to
determine a thickness gradient of a thin film to be
vapor-deposited.
Of these single action edges 11a, 11b and 11c, the first single
action edge 11a extends perpendicular to the mask movement axis A
and the second and third actions edges 11b and 11c extend inclined
at angles of +.theta.(=30.degree.) and -.theta.(=-30.degree.) to
the mask movement axis A, respectively. The single action edges
11a, 11b and 11c have their lengths each of which is sufficiently
large relative to a region of equilateral triangle 12a in the
substrate 12 on which a thin film of ternary phase-diagrammatic
system is to be formed.
It should be noted here that a single action edge generally acts in
a way as described below to develop a concentration gradient of the
thin film when it is vapor-deposited on the substrate 12.
FIG. 2 is a diagram that generally represents a single action edge
in a coordinate system in which the mask 11 has its face lying in
an x-y plane and has its depth extending in the direction of a
z-axis. As shown in FIG. 2, the single action edge, designated by
reference character 20, is made passing through the origin in the
x-y plane and extending diagonally. Also, a vector d is shown as a
normal unit vector of the single action edge 20 facing its mask
opening side. Then, the shape of the single action edge 20 is given
by a shape function as follows: d.sub.xx+d.sub.yy=0 (1)
Also, the mask opening is indicated by a mask function given by an
equation below.
.times..times.<.times..times..times..times. '.times.<
##EQU00001##
FIG. 3 is a diagram illustrating an effective movement of the
single action edge 20 of FIG. 2 that occurs when the mask is moved
in a direction as desired. Here, the moving vector of the single
action edge 20 is assumed to be m. Moving the mask edge 20 with the
moving vector m above the substrate 12 during its vapor deposition
will cause the single action edge 20 to produce a maximum film
thickness gradient in the direction of its normal vector d. For
example, three film thickness contours indicated by three types of
dotted lines in the Figure can be considered as developing. Here,
the dotted lines which are the highest, the lowest and the medium
in dot density are shown corresponding to the thickness contours
which are the largest, the smallest and the medium in film
thickness, respectively. Therefore, for any moving vector m, the
inner vector product md comes to represent an effective amount of
movement which relates to the direction in which the film thickness
gradient is the maximum or is thus an effective movement
(hereinafter referred to as such).
FIG. 4 illustrates in cross sectional views typically how a thin
film is grown changing its thickness profile with a single action
edge of a mask when the mask is moved in moving vector +m or -m. It
shows a process in which a thin film is being formed while the
single action edge 20 of the mask is having a movement +m or -m.
From the Figure in which the arrow .dwnarw. indicates a material
being vapor deposited, it is seen that the thickness gradient of a
thin film that develops does not depend on the direction in which
the mask is moved.
FIG. 5 is a graph illustrating a thickness profile function of a
thin film formed by means of a single action edge. In the graph,
the abscissa axis is taken to lie in the direction of normal vector
d of the single action edge where the vapor-deposited substrate
face and the mask face lie parallel to the x-y plane while the
z-axis (ordinate axis) is taken to lie in the direction of the film
thickness.
Here, an example is taken of laser vapor deposition and described.
Assuming that the film vapor-deposited by a single laser light
pulse has a thickness r (.quadrature./pulse), the number of laser
light pulses irradiated per unit time or laser cycle (Hz) is f, the
moving vector in is expressed by a movement per unit time (mm/sec)
or rate of moving vector, and the time for vapor deposition is
t.sub.0, the film thickness z at any position (x, y) in the x-y
plane is given by equation:
.times. '.times. ##EQU00002## where .sup.td is row vector d.
Based now on equation (3), mention is made of the thickness
gradient of a thin film formed when a first, a second and a third
single action edge 11a, 11b and 11c as shown in FIG. 1 are used.
FIGS. 6, 7 and 8 are diagrams illustrating patterns of thickness
gradient which develop in the thin film by means of the single
action edges 11a, 11b and 11c in the masking mechanism 10 in FIG.
1, respectively. In the discussion that follows, an example is
taken of the case that a ternary phase diagram is formed in the
shape of an equilateral triangle having one side perpendicular to
the direction in which the mask is moved.
The single action edges 11a, 11b and 11c have their respective
normal vectors which are expressed by column vectors in equations
below, respectively.
##EQU00003##
Substituting the row vectors of these column vectors for equation
(3) gives rise to thickness profile functions z corresponding to
the single action edges 11a, 11b and 11c, respectively, which are
in turn expressed by equations below, respectively.
.varies..varies..times..times..varies..times..times.
##EQU00004##
FIG. 6 diagrammatically shows thickness profile function z in the
case of the single action edge 11a wherein (a) indicates the film
thickness expressed by equation (5) with the darkness in black
color (the darker in black color the thicker is the film and the
less dark in black color the thinner is the film), there being also
indicated by vector B the direction in which the film thickness
becomes progressively thicker. Diagram (b) indicates the
orientation of the single action edge 11a relative to the
equilateral triangular substrate region 13, there being also
indicated by the white arrow the direction in which the single
action edge 11b is moved.
FIG. 7 likewise diagrammatically shows thickness profile function z
in the case of the single action edge 11b wherein (a) indicates the
film thickness expressed by equation (5) with the darkness in black
color, there being also indicated by vector C the direction in
which the film thickness becomes progressively thicker. Diagram (b)
indicates the orientation of the single action edge 11b relative to
the equilateral triangular substrate region 13, there being also
indicated by the white arrow the direction in which the single
action edge 11b is moved.
FIG. 8 diagrammatically shows thickness profile function z in the
case of the single action edge 11c wherein (a) indicates the film
thickness expressed by equation (5) with the darkness in black
color, there being also indicated by vector D the direction in
which the film thickness becomes progressively thicker. Diagram (b)
indicates the orientation of the single action edge 11c relative to
the equilateral triangular substrate region 13, there being also
indicated by the white arrow the direction in which the single
action edge 11c is moved.
As is apparent from FIGS. 6 to 8, the masking mechanism 10 for a
film forming apparatus as the first form of implementation of the
present invention can produce thickness gradients in, or distribute
a thickness gradient into, three different directions which are
mutually angularly spaced apart by an angle of 120.degree.. Thus, a
thin film of a ternary phase-diagrammatic system can be made by
using a different material for vapor deposition on a common
triangular substrate region 13 for each of film forming operations
by means of single action edges 11a, 11b and 11c, respectively,
acting thereon. Although a mask is shown in and described above in
connection with FIGS. 4 and 5 as being moved stepwise to form a
thin film stepwise for the sake of facilitating the understanding
of its operations, it should be noted that the mask can in actual
practice be moved continuously to form a thin film while changing
its thickness continuously.
Also, while mention is made above of a triangular substrate region
in which thickness gradients by means of single action edges 11a,
11b and 11c are superimposed to form a ternary phase diagrammatic
thin film, it will be appreciated that in the outside of such a
triangular region it is possible to simultaneously form a film of a
binary phase diagrammatic system and further to simultaneously form
a simple film composed of a single component.
In the search of a material using thin films of a ternary phase
diagrammatic system, properties of thin films of its binary phase
diagrammatic system and thin films of its single component give
auxiliary but highly useful information. Thus, the feature of the
masking mechanism 10 according to the present invention that it
permits a thin film of a binary phase diagrammatic system and a
thin film of a single component or a mono-film to be formed on an
identical substrate on which a thin film of their ternary phase
diagrammatic system is simultaneously formed is extremely useful in
the search of a material by means of a thin film of a ternary phase
diagrammatic system.
Mention is made below of binary phase diagrammatic film formed
regions and mono-film formed regions. FIG. 9 is a simulated picture
depicting in the thickness of black color the thickness
distribution of a thin film of ternary system formed on a substrate
by means of the masking mechanism shown in FIG. 1. FIG. 10 is a
diagram illustrating in the makeup of components various regions in
the thin film of ternary system shown in FIG. 9.
In FIG. 10, respective sets of dotted and solid lines shown
parallel to each other represents respective sets of film thickness
contours of the three component materials of a ternary system,
indicating that there is a concentration gradient from the dotted
line towards the solid line in each set. In an equilateral
triangular region 12a at the center of a substrate 12 where the
concentration gradients of the three component materials overlap,
there is formed a thin film of the ternary phase diagrammatic
system. Further, in equilateral triangular regions 12b, 12c and 12d
which adjoin the three sides of the equilateral triangle 12a,
respectively, and where the concentration gradients of two of the
three component materials overlap, there are formed thin films of
binary phase diagrammatic system.
Also, in regions 12e, 12f, 12g, 12h, 12i and 12j which adjoin these
regions 12b, 12c and 12d, one of two materials is deposited with a
constant thickness and while the other is deposited with a
concentration gradient, thus giving rise to thin films of,
so-called mono-gradient.
Further, in regions 12h, 12l and 12m of regions 12h, 12l, 12m, 12n,
12o and 12p which lie outside of the apexes of the regions 12b, 12c
and 12d, each of two materials is deposited with a constant
thickness while in regions 12n, 120 and 12p, one material is
deposited with a constant thickness, thus forming so-called simple
films.
It will now be appreciated that analyzing thin films of single
components in the regions 12n, 12o and 12p allows checking the
quality of the thin film of each of the components while evaluating
the mono-gradient regions 12e, 12f, 12g, 12h, 12i and 12j allows
detecting the rate of evaporation of each of the materials. To this
end, therefore, in FIG. 10 the substrate 12 during vapor deposition
can have a mask 14 mounted thereon which is separate of the mask 11
and which is formed with an unmasking aperture 14a (indicated by
the alternate long and short dash line in FIG. 10) centering around
the region 12a of the substrate 12 and larger in area than the
region 12a. Then, the thin films in the regions 12e-12p expose
their vertical sections to where the masking edges of the mask 14
define the unmasking aperture 14a, thereby facilitating measurement
of the thickness of each of thin films grown in these regions
12e-12p. For example, from
measurements of those regions of the thin films formed by first
vapor-deposition operation, the relationship between the rate of
vapor deposition and the film thickness, and the relationship
between the film thickness and concentration for each component are
known. These known data will then allow a second ternary phase
diagrammatic film vapor-depositing operation based thereon to form
a thin film precisely of a ternary phase diagrammatic system as
desired. According to this method which makes only two ternary
phase diagrammatic film vapor-depositing operations sufficient, the
time period that need be expended for the search for a ternary
material can be made short largely.
In the masking mechanism 10 in the form of implementation of the
invention described, the single action edges 11a, 11b and 11c may
generally be inclined to the direction in which the mask is moved,
at an angle of 90.degree.+.alpha..degree., an angle of
30.degree.+.alpha..degree. and an angle of -30.degree.+.alpha.,
respectively, where -90<.alpha.<90. In this case in general,
too, the normal unit vectors of the single action edges 11a, 11b
and 11c are mutually spaced apart by an angle 120.degree.,
permitting the formation of a ternary phase diagrammatic thin
film.
An explanation is next given in respect of a disk type mask moving
rotationally.
While in the previous form of implementation of the invention the
masking mechanism 10 includes the mask 11 moving linearly, a
masking mechanism may alternatively be provided that comprises a
disk type mask moving rotationally. FIG. 11 shows a rotationally
moving mask in a modification of the masking mechanism shown in
FIG. 1. This mask, designated by reference character 15, is used so
it is rotated about its center O. The mask 15 is formed with single
action edges 15a, 15b and 15c corresponding to the single action
edges 11a, 11b and 11c described previously. The first single
action edge 15a extends radially of the disk, the second single
action edge 15b extends at an angle of inclination
+.theta.(=30.degree.) to a circumferential direction and third
single action edge 15c extends at an angle of inclination
-.theta.(=30.degree.) to a circumferential direction. The single
action edges 15a, 15b and 15c have their lengths each of which is
chosen to be enough large compared to the equilateral triangular
region 12a of a substrate 12 on which a ternary phase diagrammatic
thin film is to be formed.
FIG. 12 shows, as partially enlarged, a single action edge moving
as the mask 15 is rotated. As can be seen from the Figure the
single action edge, e.g., 15a, changes the direction of its normal
unit vector with the rotation of the mask 15 to an extent that the
thickness gradient of a thin film being formed can no longer be
expressed linearly with respect to line coordinates x and y. It is
thus desirable that the disk constituting the mask 15 have a
diameter large enough that a movement of the single action edges
15a, 15b and 15c with its rotation can be approximated as a linear
movement.
Further, if the diameter of the disk constituting the mask 15
cannot be made so enough large, then a corrective method as shown
below may be used. FIG. 13 is a diagram illustrating a position on
a substrate 12 in both line coordinates (x, y) and polar
coordinates (r, .theta.) with the center of rotation O as their
origin. Since a film at a position which is identical in .theta. to
but different in r from another still has an identical thickness
and the thickness can be found from .theta., the film thickness at
that position can be accurately determined by converting the
position in line coordinate (x, y) into polar coordinates,
utilizing an equation given below.
.times..times..times..times..theta..times..times..times..times..theta..ti-
mes..times..times..times..theta..times. ##EQU00005## The center of
rotation O can be assumed to be the center of the mask 15 for the
single action edge 15a. And, for the single action edges 15b and
15c their effective center of rotation with the rotation of the
mask 15 can be assumed to be the origin of coordinates O.
Referring next to FIG. 14, an explanation is given in respect of
another masking mechanism for a film forming apparatus as a second
form of implementation of the present invention. In the Figure,
this masking mechanism, designated by reference character 30,
comprises a mask 31 supported so it can be moved forth and back
linearly along an axis indicated by arrow A. The mask 31 is formed
with unmasking openings 31e and 31f. The opening 31e has two single
action edges 31a and 31b which are designed to produce two film
thickness gradients independently of each other while the opening
31f has two action edges 31c and 31d (which are collectively
referred to as a double action edge) that are designed to act
jointly at the same time in developing a film thickness
gradient.
Here, of the two single action edges 31a and 31b and the double
action edge 31c, 31d, it should be noted that the first single
action edge 31a extends at an angle of inclination +.theta.1
(=60.degree.) to the mask movement axis A and the second single
action edge 31b extends at an angle of inclination -.theta.1
(=60.degree.) to the mask movement axis A. And, the edges 31c and
31d of the double action edge extend at angles of inclination
+.theta.2 and -.theta.2 to the mask movement axis A, respectively,
and intersect with each other at a vertical position (as shown,
lower). These single and double action edges 31a, 31b, 31c and 31d
have their lengths each of which is chosen to be enough long
compared with the equilateral triangular region 12a on of a
substrate 12 on which a ternary phase diagrammatic thin film is to
be formed.
Note, here, that the double action edge acts to develop a thickness
gradient of a thin film being vapor-deposited on the substrate 12,
as stated below. FIG. 15 is a plan view illustrating the makeup of
a double action edge. As shown, the double action edge, designated
by reference character 40, comprises edges 41 and 42 having normal
unit vectors d.sub.1 and d.sub.2, respectively, in an xy plane and
it is assumed that moving vector 111 is oriented in the direction
of -x. Then, since scalar product d.sub.1m>0 and d.sub.2m<0
there, the thickness profile produced by the double action edge 40
to a thin film being formed is described by a function which is
given by the sum of a thickness profile function according to
equation (3) for the edge 41 and a thickness profile function
according to equation (3) for the edge 42, namely by equations:
.times..times.'.times..times..times.' ##EQU00006## which can in
turn be transformed to give an equation below.
.times..times..times..times..theta..times..times..perp.'
##EQU00007## where .theta. is an angle that the normal unit vectors
d.sub.1 and d.sub.2 make and m is vector orthogonal to vector m.
From this equation it is seen that the double action edge 40
produces a maximum film thickness gradient in a direction
perpendicular to the moving vector m.
FIG. 16 is a diagram illustrating a thickness gradient of a thin
film that develops with a double action edge 40 as shown in FIG. 15
wherein (a) is a plan view of a mask having the double action edge
mask and (b) is a cross sectional view of the mask taken in a
direction perpendicular to that of the mask moving vector m, from
which it is seen that the film thickness becomes 0 at a point of
intersection of the edges 41 and 42 in the double action edge.
In contrast to this, there is also the case that the edges in the
double action edge do not intersect. FIG. 17 is a diagram
illustrating a thickness gradient of a thin film that develops with
a double action edge whose two edges do not intersect with each
other wherein (a) is a plan view of a mask having such a double
action edge and (b) is a cross sectional view of the mask taken in
a direction perpendicular to that of the mask moving vector m, from
which it is seen that in the case of a double action edge whose
edges do not intersect, there is no point produced where the film
thickness becomes 0.
Thus, in the mask mechanism 30 for a film forming apparatus shown
in FIG. 14 as the second form of the present invention, the double
action edge 31c, 31d of the mask 31 can be used to produce a film
thickness gradient of one component in a first direction which is
perpendicular to the direction in which the mask 31 is moved and
the single action edges 31a and 31b can be used to produce film
thickness gradients of the other two components in a second and a
third direction which are inclined at +120.degree. and -120.degree.
to the first direction, respectively, to form a ternary phase
diagrammatic thin film.
Here as in the first form of implementation described in connection
with FIG. 10, there can be formed such a ternary phase diagrammatic
thin film in an equilateral triangular region around the center,
and also binary phase diagrammatic thin films in regions adjacent
to the sides of the triangle and further single thin films in their
outsides.
Therefore, as in the first form of implementation described
earlier, for example, a first vapor-deposition operation may be
carried out to give rise to measurements of thin films then formed
in those regions and then to find from these measurements the
relationship between the rate of vapor deposition and the film
thickness and the relationship between the film thickness and
concentration for each component. These measured data will then
allow a second ternary phase diagrammatic film vapor-depositing
operation based thereon to form a thin film precisely of a ternary
phase diagrammatic system as desired. According to this method
which makes only two ternary phase diagrammatic film
vapor-depositing operations sufficient, the time period that need
be expended for the search for a ternary material can be made short
largely.
Referring next to FIG. 18, an explanation is given in respect of a
rotationally moving mask as a modification of the mask 31 shown in
FIG. 14. While in that form of implementation of the invention the
masking mechanism 30 is provided with the mask 31 moving linearly,
as shown it may alternatively be with a disk type mask 32 moving
rotationally. In this case, the mask 32 comprises single action
edges 32a and 32b and double action edges 32c and 32d corresponding
to the aforesaid single action edges 31a and 31b and double action
edges 31c and 31d. Of them, the first single action edge 32a
extends inclined at an angle of +.theta.1 (=60.degree.) to a
circumferential direction as a direction in which the mask is
rotationally moved and the second single action edge 32b extends
inclined at an angle of -.theta.1 (=-60.degree.) likewise to a
circumferential direction. The edges 32c and 32d in the double
action edge extend inclined at angles of +.theta.2 and -.theta.2 to
a circumferential direction, respectively.
These single and double action edges 32a, 32b, 32c and 32d have
their lengths each of which is chosen to be enough long compared
with the equilateral triangular region 12a of a substrate 12 on
which a ternary phase diagrammatic thin film is to be formed.
Further, it is desirable that the disk constituting the mask 32
have its diameter chosen large enough that changes in angular
orientation of the single action edges 32a and 32b and the double
action edges 32c and 32d with the rotation of the disk are minimum.
In this case, too, the corrective operation of linear to polar
coordinate conversion previously described in connection with FIG.
13 for the first form of implementation can be used to properly
compensate for rotary movements of the mask 32.
Referring next to FIG. 19, an explanation is given in respect of
another masking mechanism for an film forming apparatus as a third
form of implementation of the present invention. In the Figure,
this masking mechanism, designated by reference character 50,
comprises a mask 51 supported so it can be moved forth and back
linearly along an axis indicated by arrow A. The mask 51 is formed
with unmasking openings 52d, 52e and 52f, which are designed to
configure a triple action edge system in which three masks act
concurrently to produce a single film thickness gradient by means
of a triple action edge 52 comprising edges 52a, 52b and 52c
provided therein. To make up the triple action edge 52, there are
two edges 52a each of which extends perpendicular to the mask
displacement axis A and two sets of edges 52b and 52c wherein in
each set, the two edges 52b and 52c extend oppositely inclined each
other at a given angle to the mask displacement axis, and
intersecting to each other at a point. Here again, the edges 52a,
52b and 52c have their lengths each of which is chosen to be enough
large compared with the equilateral triangular region 12a of a
substrate 12 on which a ternary phase diagrammatic thin film is to
be formed.
According to the masking mechanism 50 constructed as mentioned
above, moving the mask 51 along the mask movement axis A allows the
edges 52a to produce a maximum film thickness gradient in the
direction of the mask movement axis A and the edges 52b and 52c to
produce a maximum film thickness gradient in a direction
perpendicular to the mask movement axis A. Then, if it is assumed
that z.sub.1, z.sub.2 and z.sub.3 are functions describing film
thickness profiles produced by the edges 52a, 52b and 52c,
respectively; m is movement vector of the edges 52b and 52c; m' is
the moving vector of the edges 52a; and further d.sub.1, d.sub.2
and d.sub.3 are the normal unit vectors of the edges 52a, 52b and
52c, respectively, the total film thickness profile function can
then be given by an expression below.
.times..times..times..times..times..theta..times..times..perp.''.times.'.-
times..function..times..times..theta..times..times..perp.''.times.'
##EQU00008##
In the latter equation in expression (9), it is seen that what lies
in the first bracket is a sum of a vector oriented perpendicular
to, and having a magnitude dependent on the magnitude of the moving
vector m and a vector oriented in the direction of normal unit
vector d.sub.3 and having a magnitude dependent on the magnitude of
the moving vector m'. Assuming the unit vector perpendicular to m
to be k.sub.1, the unit vector in the direction of normal unit
vector d.sub.3 to be k.sub.2 and their magnitudes to be a and b,
respectively, their compound vector v can be given by an equation
below. v=ak.sub.1+bk.sub.2 (10)
Thus, adjusting vector magnitudes a and b by suitably selecting
mask's rate of displacement m, m' allows aligning the direction of
vector v in a direction desired. Since a maximum film thickness
gradient develops in the direction of vector v, it is made possible
to produce such a film thickness gradient in a desired direction.
To with, suitably adjusting the rate of movement of the edge 52a,
m, and the rate of displacement of the edges 52b and 52c, m', it is
possible to obtain a desired film thickness gradient in a desired
direction. Therefore, selecting in and m' for each of components to
produce film thickness gradients in directions mutually angularly
spaced by an angle of 120.degree. permits forming a ternary phase
diagrammatic thin film using a single mask.
FIG. 20 is a plan view illustrating another example of making a
ternary phase diagrammatic thin film by means of a masking
mechanism as shown in FIG. 19. As shown at (a), a mask 51 formed
with a triple action edge 52 having suitably contoured is used.
These edges are indicated by A, B1, B2, C, D, E1, E2 and F below
which are indicated by arrows directions in which film thickness
gradients are produced thereby, respectively, when the mask is
moved along the mask movement axis A. It follows, therefore, that
as shown at (b) selecting these edges sequentially allows producing
desired film thickness gradients in all the directions covering
from the first to fourth quadrants to form a ternary phase
diagrammatic thin film.
While in the preceding form of implementation the masking mechanism
50 is shown comprising the mask 51 movable linearly forth and back,
it may alternatively comprise a disk type mask 53 moving
rotationally. FIG. 21 is a plan view illustrating a modification of
the masking mechanism of FIG. 19 in which the mask is constituted
by a rotationally moving mask. In this case, the mask 53 comprises
edges 53a, and edges 53b and 53c corresponding to the edges 52a and
edges 52b and 52c previously described. Of them, the edges 53a
extend inclined at an angle of +.theta.1 (=60.degree.) to a
circumferential direction in which the mask is rotationally moved,
and the edges 53b and 53c extend inclined at angles of +.theta.2
and -.theta.2 to a circumferential direction, respectively. Here
again, the edges 53a and the edges 53b and 53c have their
respective lengths each of which is chosen to be enough long
compared with the equilateral triangular region 12a of a substrate
12 on which a ternary phase diagrammatic thin film is to be formed.
Further, it is desirable that the disk constituting the mask 53
have its diameter chosen large enough that changes in angular
orientation of the single action edges 53a and the edges 53b and
53c with the rotation of the disk are minimum. In this case, too,
the corrective operation of linear to polar coordinate conversion
as in the first and second forms of implementation can be used to
obtain a precision ternary phase diagrammatic thin film.
Although in the forms of implementations described above mention is
made of the masking mechanisms as for an in-vacuum film forming
apparatus such as a laser ablation vapor deposition apparatus, this
should not be understood to be a limitation but it should be
evident that the present invention is applicable to any film
forming apparatus designed to form a thin film on a substrate by
vapor phase growth.
As will be appreciated from the foregoing descriptions, a masking
mechanism for a film forming apparatus according to the present
invention can form a ternary phase diagrammatic thin film.
Moreover, a masking mechanism for a film forming apparatus
according to the present invention requires that it comprise a
single mask and a means for uniaxially driving the mask and hence
can be made extremely small in size and volume in order to be
installed in a vacuum chamber while permitting a ternary phase
diagrammatic thin film to be made without raising the equipment
cost. Furthermore, the use of a masking mechanism according to the
present invention makes it possible to make highly reliable binary
and ternary phase diagrammatic thin films in a short period of
time.
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